Well, judging on the name, it could be looking for the source of the Service Pack 3 files. Don't remember how office updates are decompressed off hand, you might have to redownload it, and start the setup (don't complete it), to get the files to decompress. Track down the location on the hard disk, and copy them to safe folder (i.e. c:\safesp3). Reinstall office, point it to this folder.
Note that it might be a single patch that you installed as well, not just SP3, so you might have to track down SP3 patches as well.
Matt J.